An organic electroluminescence element (i.e., so-called organic EL element) using electroluminescence (referred to as EL hereinafter) of an organic material is a thin-film type completely-solid element capable of emitting light at a low voltage of several volts to several tens volts, and has many excellent features such as high brightness, high luminous efficiency, thin in thickness, and light in weight. Therefore, recently the organic electroluminescence element has attracted attention as a backlight for various kinds of displays, a display board (such as a signboard, an emergency light or the like), and a planar light-emitting body (such as a light source for a lighting fixture).
Such an organic electroluminescence element includes two layers of electrodes, and a light emitting layer formed of an organic material sandwiched between the two layers of electrodes; and the light emitted by the light emitting layer is transmitted through the electrode(s) and extracted to the outside. Thus, at least one of the two layers of electrodes is configured as a transparent electrode.
An oxide semiconductor material, such as indium tin oxide (ITO: SnO2-In2O3) or the like, or silver (Ag) is generally used as the transparent electrode. However, since ITO contains indium, which is a rare metal, the material cost goes up; and further, in order to reduce resistance, it is necessary to perform an annealing treatment at a temperature of about 300° C. to 400° C. after film-formation. Further, although silver (Ag) has excellent electrical conductivity compared with ITO, the light transmissibility will become low if the film-thickness is increased to obtain sufficient resistance.
To solve such a problem, a transparent conductive film laminate is proposed. The transparent conductive film laminate has a configuration in which a silver thin film layer composed of silver or a silver-alloy is laminated on a ground layer composed of a metal other than silver, such as gold, aluminum, copper, indium, tin, zinc or the like (see Patent Document 1, for example).